In many animals, males have evolved elaborate traits or behaviors that they use during courtship, and which are assessed by females as they choose mates. One such example is birdsong; males sing to attract mates, and females listen and seem to prefer males who sing certain kinds of songs. This project examines the development of both male singing performance and female preferences for male songs. Work with males asks how social and environmental experiences early in life influence song development. Young male swamp sparrows (Melospiza georgiana) captured from a natural population will be raised under both normal and nutritionally challenged conditions, and trained with songs in which rates of syllable repetition (trill rate) are enhanced above normal levels. These models are designed to test young males' vocal proficiency. Patterns of song learning will reveal how rearing environment shapes song structure, and thus reliably indicate male developmental history and genetic quality. Work with females asks how preferences for certain types of song develop, specifically with respect to learning as compared to inherent biases for high-performance songs. Young female swamp sparrows will be reared in the laboratory, exposed to male songs, and presented with video images of adult females giving mating displays to some of these songs. Prior work indicates that reared females learn to produce their own displays as a result this rearing methodology. Young females will then be tested for the relative roles of song quality and rearing experience in the development of their mate preferences. This project will provide new insights into the importance of experience and learning during the development of communication signals, both in their production and perception. This project includes extensive training and participation of undergraduate and high-school students.
Intellectual Merit: With funding from the NSF we investigated the development of behavior in a songbird species, the swamp sparrow (Melospiza georgiana). In particular we examined how young females develop mate preferences, and how young males develop the ability to sing and to maximize their vocal performances. Female mate preference is a crucial component of sexual selection, yet we have limited knowledge of how it develops. Mating preferences in adults may be shaped by multiple factors during development including genetic predispositions, social copying, and learning. We studied female preference development in swamp sparrows, a species in which adult females are known to prefer songs characterized by high vocal performance. In two experiments, we raised and tutored females with song models of normal performance. We then employed a new training method in which we presented young females with tutor songs paired with videos of adult females giving copulation solicitation displays (CSD), with the idea that this method would stimulate developing females to then perform CSDs upon maturity.. When birds reached breeding condition, we tested female preferences, using the CSD assay, for familiar tutor songs against novel songs, and against higher- and lower-performance versions of tutor songs.. In the first comparison, females gave significantly more CSDs to tutor songs than to novel songs. In the second comparison, females gave significantly fewer CSDs to low-performance songs than to tutor songs, and also responded the most strongly to tutor songs overall. A greater response to tutor songs in both experiments implicates a strong influence of experience in shaping female preference, although preference appears to also be driven by innate biases in favor of higher performance. These experiments provide the first evidence that female preference development is guided by an interplay of learning and innate biases for elaborate or intricate sexually selected traits. We also investigated mechanisms of song learning in male swamp sparrows. We trained males with low-performance songs, asking whether males might memorize and then elevate these songs to their individual levels of vocal proficiency. We found that males readily learned low-performance tutor songs but, as predicted, reproduced these songs with higher levels of vocal performance, more in line with their own presumed abilities (Lahti et al. 2011). We also found that the lowest-performance tutor songs were either copied inaccurately or not at all, suggesting perceptual or memory biases against such songs models. We have conducted an experiment asking how nutritional stress affects males’ ability to learn and reproduce high-performance songs. We raised males under normal and nutritionally stressed conditions, and challenged them with high-performance and control tutor songs. Analyses completed so far indicate that song performance levels and learning abilities vary widely among males. Further, we have conducted in vivo neural recordings of song centers in these same birds, in collaboration with Dr. Remage-Healey (UMass Psychology). Analyses completed to date suggest that males who learned tutor songs with greater accuracy also show greater selectivity in their neural responses (responding more strongly to presentation of learned songs than to novel or unlearned songs), indicating persistent memory in song nuclei regions of the brain. This work will explore the connection between neural responses, male song quality, and male quality. Broader Impacts: We trained over 27 undergraduates in animal care methods, and have advised twelve independent study and research apprentice undergraduate projects, in which students conducted research and analyzed data. Three students have presented their work at research symposia and one student conducted a senior thesis project. We visited K-5 schools as part of an outreach program to bring science to inner-city schools, and also participate in a community outreach program "OEB's Science Cafe", which hosts speakers for the local community in order to have a science-based discussion.
